I have some time on a RC390 that a friend has, and it's OK, but it's on its second engine with under 4000 mi.My husband has been riding for nearly 4 decades and has had many different bikes during that time - everything from adventure touring to dirt bikes to sport bikes. We just sold his Panigale 1199 because he no longer wanted a super sport. We also sold the KTM 640 at the same time. He replaced them with a KTM 690 SMC-R. Since he's always enjoyed flicking my Ninja 300 around the few times I've let him ride it, we've decided to add another small CC bike to the garage in the spring. He hasn't decided if he's going to with a Yamaha R3, a KTM 390, or a Ninja 400. Either way, it won't be anything over 400 cc.
As others have said, there isn't a 'beginner' bike, there's small cc and large cc - and a rider never outgrows a motorcycle. They may decide they want something else, but it's certainly not because their skill is so awesome that the bike no longer meets their expectations; it's always because we want something else.